#include <iostream>
#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    int p,i=1,k=0;
    fin>>p;
    while(i<=p)
    {
        k=k+i;
        i=i*5;
    }
    fout<<(p*i)/k;
    return 0;
}